you have to open up the case and screw everything apart / back together. no desoldering/ soldering is required. it is only screws, but still nothing you would want to do during a gig, or something. the controll board is an easy build and doesn`t have much expensive components – if you have to filterboards – just build 2 shruthis.

you can also connect more than one filterboard, but that requires you to build a new case (or get a Shruthi XT from fcd72). You could also put some switch to switch the connections from one filter to the other

I just came up with the idea and I’m not sure it is feasible:
the filter board hosts the power related part (that’s where you plug your DC adapter in) and the audio ins and outs, but connects to the control board for everything else. Depending on the filter you have 8 wires that connect it to the control board, 2 of them of course 2 of them are used for the power.
So theoretically you just need a switch that has enough poles, you connect both filter boards to the switch, so you can actually switch from one to the other. You’ll have to reboot the shruthi and set the correct filter in the fimware though every time, but it’s a lot easier than having to open the case and replace the filter manually.
I don’t know if such a thing as an 8 pole switch exists, but if not you could probably build something to act like one.

of course you’d have to connect the power plug to both filter boards and have 2 audio ins and 2 audio outs on the box (and you have to change the cables from one to the other.

I know that on Frank’s Shruthi programmer you can attach two filters (not all combinations are supported) this makes it possible to route the signal from the control board to two filters in parallel. I guess one could use that circuitry (or a part of it) to make something where you can use both filters or just one, without the programmer part.
though getting the programmer is probably the best solution anyway! :)